scsi: qla4xxx: skip error recovery in case of register disconnect.

A system crashes when continuously removing/re-adding the storage
controller.

Signed-off-by: Manish Rangankar <manish.rangankar@cavium.com>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>